...Now, judiciary can only be as good as the evidence providing-machinery, which largely happens to be the police force. Plus, there are possibilities to influence judges by enticing/threatening with promotions/transfers & illegal money from powerful people. If not too risky judges would use their 'discretion' to benefit the powerful party (of the accused & the defendant) to gain benefits in return.
Now, what a deadly & effective combination this is for justice to not be delivered when powerful people are involved!
3. Lack of resources/manpower/proper training. Many crime scenes are not even properly sealed as can be seen on TV. I guess, these are not to help the criminals evade, but because of lack of professionalism/training.
All the Indian states are in acute shortage of policemen. Part of the cause is apathy of governments, but there is another important cause, which we tend to neglect - India is an economically poor country. Even the constables currently employed are paid very poorly despite very heavy workload. This creates perfect environment for them to take bribes & manipulate evidence when required. But moreover, governments do not recruit more police personnel simply because they do not have the funds! One might cynically say that if politicians would stop amassing wealth for themselves, more policemen could be recruited. That would be oversimplification. In all likelihood, to recruit 3 constables, a doctor would have to be removed from job, or 2 teachers, or hundreds of farmers would lose quintals of fertilizers. Would that be acceptable?
Likewise, appointments & promotions of new judges are not being made despite so many pending cases. Again part of the reason is the same - we do not want to deprive people of doctors, teachers or farmers of fertilizers. This makes our judiciary exquisitely slow, of course, apart from other disincentives to work in a fair way that I mentioned.
Now coming to a very important question you have asked, "We tried and punished B&R based on that evidence. ... Why won't we try the guilty for 1984 etc, then?"
Let me enlist the possible reasons (applies to all the cases of rioting & not just 1984):
1. Nexus between politicians, police & to some degree, judiciary. Those who had encouraged these crimes or benefitted from them are having the greatest (indirect) power to determine whether to punish their accomplices or not! Can I put it more simply?...